As shown in FIG. 1, an article of prior art roller skate is provided with a sole plate 1 which is in turn provided in the front end thereof and the rear end thereof with a protruded portion 2. A sole 3 is attached to the underside of the sole plate 1 and is provided with two receiving cells 4 corresponding in location to the protruded portions 2 of the sole plate 1. Two roller seats 5 are provided with a roller base seat 6, a pivoting seat 7 mounted on the roller base seat 6, and a roller 8 mounted on the pivoting seat 7. The two roller base seats 6 are located in the receiving cells 4. The roller 8 can be extracted out of or retracted into the sole 3 for skating or walking. When the roller 8 is jutted out of the sole 3, the pivoting seat 7 is in contact with the protruded portion 2 of the sole plate 1 so as to support the body weight of a wearer of the prior art roller skate.
Such a prior art roller skate as described above is defective in design in that the roller is extracted out of or retracted into the receiving cell 4 with finger, which is thus prone to become dirty. In addition, the diameter of the axle of the roller 8 is limited by the thickness of the pivoting seat 7, thereby resulting in the incompatibility of the axle with the rollers of various sizes. Moreover, the height of the roller 8 can not be appropriately adjusted to enable the prior art roller skate to be used effectively as a walking shoe as well as a roller skate.